1. Field of the Invention
This invention relates to spread spectrum communications. More specifically, this invention relates a filter and use of long, scalable, separable PN sequences to achieve variable communication rates together with low complexity in spread spectrum communications.
2. Description of Related Art
A variety of spread spectrum communications systems are well known in the art. Often these systems use very long PN codes to achieve processing gain. However, typically, such prior systems have substantial problems with coherence and frequency error and such problems interfere with achieving the objective of robust spread spectrum communications. Typically, these prior systems also require large matched filters to despread signals, where the use of correlators is inappropriate.
Although the following cited U.S. patent documents are not necessarily “prior art,” the reader is referred to the following U.S. patent documents for general background material. Each of these patents is hereby incorporated by references in its entirety for the material contained therein.
U.S. Pat. Nos. 4,351,064; 4,953,178; 4,977,578; Re. 33,875; 5,319,672; 5,400,359; 5,471,509; 5,737,368; 5,740,096; 5,790,588; 5,790,590; 5,815,055; 5,881,099; 5,909,461; 5,912,644; 5,926,512; 5,974,082; 5,991,332; 6,031,415; 6,104,746; 6,128,332; 6,154,482; 6,154,487; 6,212,219; 6,233,272; 6,265,807; 6,317,452; 6,331,998; 6,333,925; 6,356,555; 6,434,185; 6,493,334; 6,493,376; 6,549,567; 6,556,621; 6,560,270; 6,560,271; 6,567,017; 6,570,865; 6,580,750; and 6,590,881.